Please Boot to the System Recovery Options
If you have Windows 7 installation disc, just insert a DVD to the drive, restart computer and it should load automatically (option two presented in the article).
It's possible also that your computer has a pre-installed recovery partition instead - in such a case use a method one (by pressing F8 before Windows starts loading)...NOTE. If none of the above apply you can create System Repair Disc (link in "Option two") and boot from it.

On the System Recovery Options menu you will get the following options:

Startup Repair

System Restore

Windows Complete PC Restore

Windows Memory Diagnostic Tool

Command Prompt

Choose Command Prompt
You should see X:\SOURCES>...

Execute the following commands in bold.
Press Enter after every one of them.

I booted with the cd and when it reached the end of booting the cd I get blue sceen with this message:

A problem has been detected and windows has been shut down to prevent damage to your computer.

If this is the first time you've seen this stop error screen, restart your computer. If this screen appears again, follow these steps:

Check for viruses on your computer. Remove any newly installed hard drives or hard drive controllers. Check your hard drive to make sure it is properly configured and terminated. Run CHKDSK /F to check for hard drive corruption, and then restart your computer.

I'm not sure what to think at this moment.
Possibly we're dealing with something more than just infection.

We can't boot the computer from any external source.

Run hard drive diagnostics: http://www.tacktech.com/display.cfm?ttid=287
Make sure, you select tool, which is appropriate for the brand of your hard drive.
Depending on the program, it'll create bootable floppy, or bootable CD.
If downloaded file is of .iso type, use ImgBurn: http://www.imgburn.com/ to burn .iso file to a CD (select "Write image file to disc" option), and make the CD bootable.

NOTE. If your hard drive is made by Toshiba, unfortunately, you're out of luck, because Toshiba doesn't provide any diagnostic tool.